I'll check grit when I get home tonight, all I know is that the package said "Ultra-Fine" and that it took off very little plastic, so for the deeper gouges it took awhile. As for prying the case apart, it isn't difficult, it's just that the pieces click together and so they resist a little as you are prying at them. I seem to remember that applying some gentle top to bottom pressure on the back of the housing helped.

I probably should add that it's definitely easier to be adventurous with a housing when you already have one and the one you're working on is in the worse shape of the two.